The present invention relates to a device for continuously regulating the erection of a drive tandem axle of a vehicle or a self-moving working machine having a vehicle frame and at least one drive axle, wherein a drive tandem axle having a movable tandem axle housing is respectively disposed at the ends of the drive axle, and the torque introduced by the drive axle is mechanically distributed through the drive tandem axle to the wheels disposed in the tandem axle housing. The invention further relates to a method for continuous regulation of the erection of a tandem axle of a vehicle or a self-moving working machine.
Such devices for regulating the erection of a drive tandem axle of a vehicle or a self-moving working machine are known. Tandem axles or also boogie axles have the disadvantage that the axle beam erects more or less independently of transmission ratios and the geometrical ratios when a torque is introduced. Thereby, non-uniform distribution of the wheel load between the front and rear wheels results, which are disposed at the respective ends of the axle beams.
Thereby, it occurs that at least one of the wheels loses road grip or the load on soil is greatly reduced, respectively. Since the described tandem axles are mainly used in forest machines, tipping trucks and graders, which especially operate in pathless terrain, this results in great restrictions during operation of the corresponding vehicles and in different tire wear.
In order to prevent the mentioned erection effect, in known devices, a transmission of 1:1 or nearly 1:1 is used in the axle beam. However, this is disadvantageous in that the components within the axle beam have to transmit a high torque and thus are appropriately largely dimensioned. Therefore, such axle beams become very expensive, heavy and lose ground clearance. Further known devices for preventing an erection effect of a tandem axle use a double planetary gearing or a measuring gearing and use the back torque thereof to reduce the erection effect. Corresponding devices are described in DE-A1-19802371 and in DE-A1-4120801. However, these devices are disadvantageous in that the back torque is not able to be adjusted in its magnitude and is always proportional to the input torque. An erection effect, which can also be desirable in some driving situations, is not able to be caused. The front or rear wheel of the tandem axle, respectively, is not able to be intentionally lifted by this mechanism.
Another device known from the prior art is described in DE-A1-19616405. This device uses hydraulic cylinders attached externally between a tandem box and the vehicle frame and pressurized with pressure that is switched proportionally to the operational pressure of a driving hydraulic motor. However, this is disadvantageous in that the external hydraulic cylinders are susceptible, since they are exposed to the environmental influences. Additionally, the installation between vehicle frame and tandem beam is expensive and restricts the independent freedom of movement of the tandem axle. Distinct control of the left and right sides is not possible.
Finally, DE-U1-20217910 describes a device for regulating the erection of a tandem axle, wherein a housing of a pressurizable rotary piston cylinder is fixedly connected to an axle housing of a drive axle, and a movable piston of the rotary piston cylinder drives a succeeding planetary gearing having a planetary axle and planet pinions, wherein the planetary axle of the planetary gearing is fixedly connected to the axle housing or the housing of the rotary piston cylinder, and the planet pinions act on a toothed wheel connected to a tandem axle housing. By interposing a rotary piston cylinder and the planetary gearing succeeding the rotary piston cylinder, it is possible to exert a predefined pressure on the tandem axle housing and to either counteract an erection effect of the tandem axle or to perform active lift of the tandem axle. Therein, the rotational direction of the rotary piston is reversed by the planetary gearing upon pressurization such that corresponding counter-torques act on the tandem axle housing. However, this device is disadvantageous in that also herein the predefined and controllable pressure is always in a fixed ratio to a theoretically occurring erection torque. Separate regulation of the erection effect of the individual tandem axles considering the respectively occurring actual torques is not possible.
Therefore, it is the object of the present invention to provide a device and a method for continuous regulation of the erection of a tandem axle of a vehicle or a self-moving working machine, which reliably prevents the unwanted erection of the tandem axle to a predeterminable extent on the one hand, and allows for separate regulation of the erection effect of the individual tandem axles considering the respectively occurring actual torques on the other hand.
This object is solved by a device and a method for continuous regulation of the erection of a tandem axle having the features of the independent claims 1 and 11.
Advantageous developments are described in the respective dependent claims.